The Small Computer Systems Interface SCSI! bus is used extensively for computer peripheral devices. It is designed for use with hard drives, tape drives, scanners, CD Roms, printers and computers. Indeed, all computers from small personal computers to workstations to mainframes are equipped with SCSI interfaces.
It is often necessary to connect multiple numbers of computers to multiple numbers of SCSI peripheral devices. Connection of an SCSI device to a computer equipped with an SCSI interface is point to point through a standard SCSI cable a few meters in length. Hence the conventional means of accessing an SCSI device is accomplished through the computer to which the SCSI device is attached. Clustering of these SCSI devices requires a Local Area Network LAN! switch that connects the computers where the SCSI devices are attached through Network Interface Cards NICs! which are installed within the computers.
The use of LAN switches and these interface cards increases the cost and complexity of interconnecting multiple computers to multiple peripheral devices. Moreover, such use greatly reduces the speeds of interconnection. For example, the most widely used LAN interface, fast Ethernet, has a maximum speed of 200 megabits per second, whereas SCSI devices are capable of speeds up to 320 megabits per second. In the aforementioned copending application, a new type of high speed switch is introduced which not only permits the peripheral devices to be operated at their maximum speeds, but also eliminates the need for LAN switches and interface cards.
However, it is often necessary for host computers and peripheral devices to be interconnected under conditions when the devices are disposed remotely, perhaps on the order of kilometers of separation, from the host computers. Under these conditions, a Wide Area Network, WAN! is employed in establishing such interconnections. The WAN routers employ network layers which increase cost and complexity of the system. Moreover, WAN connections employ interconnection speeds which are limited to a few megabits per second. This sharply degrades the SCSI speed capability of 320 megabits otherwise available for use in the system.
In the present invention, the WAN connections and routers are eliminated, and a switch fabric is substituted which utilizes remotely disposed switches optically interconnected through optical transceivers which are capable of moving data in gigabits per second speed. As a result, the cost and complexity of the system is much reduced while the transmission speed is greatly increased.